Emission standards are requirements that set specific limits to the amount of pollutants that can be released into the environment. Many emission standards focus on regulating pollutants released by automobiles and other powered vehicles but they can also regulate emissions from industry, power plants, and small equipment such as lawn mowers and diesel generators. Standards generally regulate the emissions of nitrogen oxides (NOx), sulfur oxides (SOx), particulate matter (PM), carbon monoxide (CO), volatile organic compounds (VOCs) and other pollutants. According to the Environmental Protection Agency, nonroad diesel engines contribute greatly to air pollution in many of the nation's cities and towns.
In recent years, standards have been established to reduce emissions from nonroad diesel engines which traditionally met relatively modest emission requirements. The first federal standards (Tier 1) for new nonroad (or off-road) diesel engines were to be phased in from 1996 to 2000. Increasingly more stringent Tier 2 and Tier 3 standards for all equipment had phase-in schedules from 2000 to 2008. Tier 4 standards are to be phased in over the period of 2008-2015 and require that emissions of PM and NOx be further reduced by about 90%.
The new standards apply to diesel engines used in industries such as construction, agricultural, and mining and are designed to reduce emissions from nearly every type of diesel vehicle and equipment. The standards are phased in over several years to provide adequate lead time to engine and equipment manufacturers. It is estimated that over 650,000 pieces of nonroad diesel equipment sold in the United States each year will be covered by the new standards. Currently about six million pieces of nonroad diesel equipment are in use in the United States.
The new emission standards for PM and NOx which can be found in EPA Publication 420-F-04-032 (May 2004) are tabulated below.
Final Emission Standards (g/hp-hr)First YearStandardsRated PowerApplyPMNOxhp < 25 20080.30—25 ≦ hp < 7520130.023.5 (includes nonmethanehydrocarbons) 75 ≦ hp < 1752012-20130.010.30175 ≦ hp < 7502011-20130.010.30hp ≧ 7502011-20140.0752.60.50 gensetsover 1200 hp20150.02 gensets;0.50 all gensets0.03 all engines
Specifically, Tier 4 emission standard for engines, to be phased-in from 2008-2015, introduce substantial reductions of NOx (for engines above 56 kW) and PM (above 19 kW), as well as more stringent HC limits. CO emission limits remain unchanged from the Tier 2-3 stage. In engines of 56-560 kW rated power, the NOx and HC standards are phased-in over a few year period. The initial standards (PM compliance) are sometimes referred to as the “interim Tier 4”, “Tier 4i”, “transitional Tier 4” or “Tier 4 A”, while the final standards (NOx/HC compliance) are sometimes referred to as “Tier 4 B”. As an alternative to introducing the required percentage of Tier 4 compliant engines, manufacturers may certify all their engines to an alternative NOx limit in each model year during the phase-in period. These alternative NOx standards are:                Engines 56-130 kW:                    Option 1: NOx=2.3 g/kWh=1.7 g/bhp-hr (Tier 2 credits used to comply, MY 2012-2013)            Option 2: NOx=3.4 g/kWh=2.5 g/bhp-hr (no Tier 2 credits claimed, MY 2012-2014)                        Engines 130-560 kW: NOx=2.0 g/kWh=1.5 g/bhp-hr (MY 2011-2013)        
The disclosed device and method enables an operator to move a cooling medium across the cooling tubes of a heat exchanger to promote a cooling effect on diesel engines which do not rely on ram-air for cooling purposes like a typical motor vehicle capable of being used on roads and highways. The disclosed device and method utilize a venturi in the exhaust line to draw the cooling medium through the system.
Although prior art systems exist, the present device and method eliminates or reduces the requirement for multiple conduits and connections thereby providing for a cleaner, less complicated packaged installation. The design of the system described herein results in a more reliable system and potential cost savings in the manufacture thereof. Advantageously, emissions are reduced and fuel usage is reduced.
U.S. Pat. No. 6,848,433 utilizes a venturi in the cooling medium inlet. A fluid cooling system comprises a heat exchanger having a pressure differential between an inlet area and a cooling area. A venturi is configured between the areas to enhance flow of a cooling medium from the exchanger output which is connected to an exhaust pipe.
U.S. Pat. No. 7,322,192 discloses an internal combustion engine having an exhaust gas recirculation (EGR) system. The system includes an air-to-gas EGR cooler, an air inlet line communicating cooling inlet air to the EGR cooler, an EGR supply line communicating exhaust to the EGR cooler, a venturi in the exhaust circuit, and an air outlet line communicating heated air from the EGR cooler to the venturi. Flow of exhaust through the venturi draws cooling air through the EGR cooler. The EGR system also includes a turbocharger having an exhaust turbine and an inlet air compressor. A compressor outlet circuit communicates air from the compressor to an engine air intake. A valve is located in the compressor outlet circuit. An EGR venturi in the compressor outlet circuit is connected in parallel with the valve. A cooled EGR line communicates cooled exhaust from the EGR cooler to a suction port of the EGR venturi.
U.S. Pat. No. 7,322,193 discloses an exhaust gas recirculation (EGR) system for an internal combustion engine having a combustion air intake circuit, an exhaust manifold, and an exhaust circuit for communicating engine exhaust to the environment. The EGR system includes an air-to-gas EGR cooler, an air supply conduit for supplying inlet air to the EGR cooler, an EGR supply conduit for communicating exhaust from the exhaust circuit to the EGR cooler, and an EGR outlet conduit communicating cooled EGR from the EGR cooler to the intake circuit. The EGR system also includes a venturi unit in the exhaust circuit, and an air outlet conduit communicating heated air from the EGR cooler to the venturi unit. Flow of exhaust through the venturi creates a pressure which draws cooling air through the EGR cooler. A valve controls flow through the outlet conduit as a function of a sensed temperature in the intake circuit.
The prior art referenced above feature an enclosed heat exchanger, a venturi unit in the exhaust circuit, a multiplicity of hoses and connectors in communication with the heat exchanger and associated equipment. Specifically, the prior art devices feature at least four points of connection with the heat exchanger. These are 1) the cooling medium inlet, 2) the cooling medium outlet, 3) the inlet for the medium to be cooled and 4) the outlet for the medium to be cooled. None of the prior art references disclose a system having a reduced number or conduits and connections thereby providing for a less complicated, yet effective means of cooling the medium by means of drawing ambient air through the system's heat exchanger.